The invention relates to a mounting mechanism for enclosure of an electrical unit, and more particularly to such mechanism which provides an electrical connection between a conductive enclosure having an insulating coating and a conductive, parts-carrying baseplate as a conductive screw is used to mount the enclosure on the baseplate.
In electrical units such as tape recorders of a reduced size, in particular, of a miniature size, circuit components and drive parts are mounted on a conductive baseplate, which is then received in an enclosure such as the recorder casing. To avoid electrical contact between the components and the enclosure, the latter is either formed of an insulating material or formed of a conductive material with an insulating coating layer over the entire surface thereof. In order to provide the shielding effect which prevents adverse influences upon the internal electrical circuit of external electric or magnetic fields, the enclosure is electrically connected with the baseplate.
Referring to FIGS. 1 and 2 which show prior art arrangements to make such electrical connections there is shown a conductive baseplate 1 on which parts are to be mounted. a conductive post 2 is fixedly mounted on the baseplate with its upper end formed with a threaded bore 3, into which a conductive headed screw 6 is fitted, with an enclosure 4 having an insulating coating 5 disposed between the head of the screw and the post and the screw extending through an opening 4a formed in the enclosure. In this manner, the conductive enclosure 4 is secured to the baseplate 1. To provide an electrical connection between the enclosure and the baseplate, the coating 5 is previously removed in a region a of the enclosure 4 which is adapted to engage the post 2. Alternatively, the insulating coating is previously removed in a region b of the enclosure 4 which is adapted to engage the bottom surface of the head 6a of the screw 6, which joins the threaded body 6 as shown in FIG. 2.
However, with the techniques illustrated in FIGS. 1 and 2, the insulating coating 5 must be previously removed from the enclosure 4 before the screw is set in place. The removal represents a troublesome operation, and there is also a likelihood that the enclosure may be mounted in place without previously removing part of its insulating coating. If one fails to remove the coating, it is very difficult to notice such failure of removal without disassembling the connection. In addition, a region of the enclosure from which the insulating coating is removed may be exposed externally to the elements which may degrade the appearance or may give rise to the occurrence of rust.